EF Core 和 SQL 多级联

Question

我正在尝试使用 SQL Server 在 ef-core 中对付款进行建模。支付有一个从方和一个到方，在这种情况下说每个用户或参与者。我有一个与 FromActor 和 ToActor 有关系的事务类。生成的迁移在数据库中更新失败，说明可能有多个级联路径。我已经读到我需要在 db 上下文中覆盖 OnModelCreating 方法中的默认级联，但我不确定如何。对 EF 和迁移相当陌生，我只是关注 https://docs.microsoft.com/en-us/ef/core/get-started/overview/first-app?tabs=visual-studio。

public class Actor
{
    public int ActorId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public List<Transaction> Transactions = new List<Transaction>();
}

public class Transaction
{
    public int TransactionId { get; set; }
    public DateTime TimestampUtc { get; set; }
    public decimal Amount { get; set; }
  
    public int FromActorId { get; set; }
    public Actor FromActor { get; set; }
    public int ToActorId { get; set; }
    public Actor ToActor { get; set; }
}

在表“事务”上引入 FOREIGN KEY 约束“FK_Transactions_Actors_ToActorId”可能会导致循环或多个级联路径。指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他 FOREIGN KEY 约束。

您能告诉我如何在 db 上下文中进行这项工作吗？还是我需要对我的域进行不同的建模？

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        ??
    }

更新：根据我在这里收到的所有 cmets 是我最终的工作解决方案 -

public class Actor
{
    public int ActorId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public virtual List<Transaction> FromTransactions { get; set; }
    public virtual List<Transaction> ToTransactions { get; set; }
}

public class Transaction
{
    public int TransactionId { get; set; }
    public DateTime TimestampUtc { get; set; }
    public double Amount { get; set; }
    
    public int FromActorId { get; set; }
    public virtual Actor FromActor { get; set; }
    public int ToActorId { get; set; }
    public virtual Actor ToActor { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Transaction>(entity =>
        {
            entity.HasOne(t => t.FromActor)
                .WithMany(a => a.FromTransactions)
                .HasForeignKey(t => t.FromActorId)
                .OnDelete(DeleteBehavior.NoAction)
                .HasConstraintName("FK_Transaction_Id_From_Actor");
            entity.HasOne(t => t.ToActor)
                .WithMany(a => a.ToTransactions)
                .HasForeignKey(t => t.ToActorId)
                .OnDelete(DeleteBehavior.NoAction)
                .HasConstraintName("FK_Transaction_Id_To_Actor");
        });

        Seed(modelBuilder);
    }

    private void Seed(ModelBuilder modelBuilder)
    {
        using (var reader = new StreamReader("Data/Actors.csv"))
        using (var csv = new CsvReader(reader, CultureInfo.InvariantCulture))
        {
            var actors = csv.GetRecords<Actor>();
            modelBuilder.Entity<Actor>().HasData(actors.ToArray());
        }
    }

protected async Task<Transaction> SaveTransactionAsync()
    {
        using (var context = contextFactory.CreateDbContext())
        {
            var transaction = new Transaction()
            {
              TimestampUtc = DateTime.UtcNow,
              Amount = 20.45,   // hardcoded for illustration
              FromActorId = 1,  // hardcoded for illustration. Using id from actor seed file.
              ToActorId = 2,    // hardcoded for illustration. Using id from actor seed file.
            };
            context.Add(transaction);
            await context.SaveChangesAsync();
            await context.Entry(transaction).Reference(t => t.FromActor).LoadAsync();
            await context.Entry(transaction).Reference(t => t.ToActor).LoadAsync();
            logger.LogDebug("Saved transaction to database.");
            return transaction;
        }
        
    }

除了禁用删除级联之外，主要的教训是我必须为 Actor 引入 2 个集合（从和到）。而且我无法在保存期间设置事务的 FromActor 和 ToActor 属性；只设置ID。设置对象会在事务保存期间尝试插入到 Actors 表中。不直观。

感谢您的帮助。

Answer 1

您可以使用 modelBuilder 以您想要的方式为每个实体修改模型构建器的属性是的：

如果我要给你举个演员的例子，可能是：

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<Transaction>(entity =>
            {
                entity.HasOne(t => t.FromActor)
                    .WithMany(a => a.TransactionsFrom)
                    .HasForeignKey(t => t.FromActorId)
                    .OnDelete(DeleteBehavior.NoAction)
                    .HasConstraintName("fk_transaction_from_id_from_actor");
                entity.HasOne(t => t.ToActor)
                    .WithMany(a => a.TransactionsTo)
                    .HasForeignKey(t => t.ToActorId)
                    .OnDelete(DeleteBehavior.NoAction)
                    .HasConstraintName("fk_transaction_to_id_to_actor");
            });
    }

或类似的东西。如您所见，语法非常不言自明。

public class Actor
{
    public int ActorId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    #region InverseProperty
    public ICollection<Transaction> TransactionsFrom {get; set; }
    public ICollection<Transaction> TransactionsTo {get; set; }
    #endregion InverseProperty
}

public class Transaction
{
    public int TransactionId { get; set; }
    public DateTime TimestampUtc { get; set; }
    public decimal Amount { get; set; }
  
    public int FromActorId { get; set; }
    public int ToActorId { get; set; }

    #region ForeignKey
    public virtual Actor ToActor { get; set; }
    public virtual Actor FromActor { get; set; }
    #endregion ForeignKey
}

实体Transaction有一个Actor FromActor，那个FromActor有一个交易列表（TransactionsFrom）。外键应该是 FromActorId，并且在删除时，您不对实体执行任何操作。约束的名称应该是“fk_transaction_id_from_actor”。

这允许您随意更改约束、行为和命名。如果需要，它还可以允许您通过迁移在模型中添加数据：

modelBuilder.Entity<Actor>().HasData(
                new
                {
                    ActorId = 1,
                    FirstName = "John",
                    LastName = "Doe"
                },
                new
                {
                    ActorId = 2,
                    FirstName = "Jane",
                    LastName = "Doe"
                });

当您执行“dotnet ef migrations add myMigration”时，上下文中的每个更改都将在下一次迁移中注册，因此如果您在 HasData 中添加数据，并且您不是单独处理项目，请务必跟踪 id 否则迁移将失败！ 我希望这足以帮助你。

Answer 2

你必须为你的类添加一些导航属性

public class Actor
{
    public int ActorId { get; set; }
     .....

    public virtual List<Transaction> FromActors {get; set;} 
   public virtual List<Transaction> ToActors { get; set; }

}

public class Transaction
{
    public int TransactionId { get; set; }
    ....

    public int? FromActorId { get; set; }
    public  virtual Actor FromActor { get; set; }

    public int? ToActorId { get; set; }
    public virtual Actor ToActor { get; set; }
}